Question: how do black holes form ?

Claire Greenwell answered on 11 Mar 2019:

There are two types of black hole – “stellar mass” black holes, that are about 10 times the mass of the Sun, and “super massive” black holes, which are about a million to a billion times the mass of the Sun.

Stellar mass black holes are formed when large enough stars reach the end of their lives and explode. What’s left over is the black hole. (Hannah’s written a really good explanation of those explosions – called supernovae – here /timem19-zone/question/black-holes-are-caused-by-stars-exploding-due-to-their-fuel-but-how-does-the-fuel-decrease-but-cause-it-exploding/)

And actually we still don’t really know how super massive black holes get to be so big! We can see that they have existed since the really early days of galaxies in the universe, but we’re still not sure how they evolved!